1. Field of the Invention
The present invention relates generally to a system for use in information apparati such as computers and measuring apparati, for specifying coordinates of a body in three-dimensional space, and more particularly, it relates to an improvement in a technique for specifying coordinates of a body by using radiation of light and the like.
2. Description of the Related Art
With the development of electronic technology in the field of computers etc., systems employing three-dimensional space have been increased in number. The most typical one of such systems is the virtual reality (hereinafter referred to as "VR") system.
The VR system enables a person to have a similar experience in artificial reality to a real experience. The following literatures describe such virtual reality:
(1) "Virtual Environment" by Michitaka Hirose, Proceedings of the 6th Human Interface Symposium (1990);
(2) "Generation of Artificial Reality" by Michitaka Hirose, System/Control/Information, vol. 33, No. 11, pp. 590-597 (1989); and
(3) "How Far Virtual Reality Will Be Realized" by Michitaka Hirose, Journal of the Japan Society of Mechanical Engineers, vol. 93, No. 863, pp. 72-78 (1990)
For the VR system, it is essentially important to input a position and posture of a person to the system with accuracy and at a high speed. Various attempts have been made to accurately specify coordinates of a person at high speed.
FIG. 1 shows one example of such a VR system employing coordinate input system. The system is described in the above-described literature (1).
With reference to FIG. 1, the VR system includes a space sensor 102 attached to the head of a person 100, liquid crystal glasses 104 which the person 100 puts on, a data glove 106 which the person 100 puts on his hand, a space sensor controller 108 for controlling the space sensor 102, a data glove controller 110 for controlling the data glove 106, a graphics and world controller 112 for subjecting a world model 128 to predetermined processing to adapt virtual reality to the person's movements according to a position and posture of the person and a position and posture of his finger input respectively from the space sensor controller 108 and the data glove controller 110, a stereo display controller 114 for producing video to be applied to the person 100 based on the world model 128, a stereo display 116 for performing stereoscopic display of a virtual body 118 in response to a signal applied from the stereo display controller 114, a synchronization signal transmitter 126 for alternately opening/closing right and left liquid crystal shutters of the liquid crystal glass 114 in synchronization with a display cycle of the virtual body 118 in response to a synchronization signal from the stereo display controller 114, a halfmirror 120 disposed in front of the person 100, and a force feedback controller 124 for controlling a force feedback head 122 such that force is applied against the data glove 106 and the hand of the person 100 according to the world model 128.
The VR system shown in FIG. 1 operates as follows. The space sensor 102 and the space sensor controller 108 detects position/posture of the head of the person 100 and applies their three-dimensional coordinates to the graphics and world controller 112. The data glove controller 110 detects movements of the person's (100) hand and applies information indicative of the posture and the position of the hand to the data glove controller 110. The data glove controller 110 processes the signal to generate a signal indicative of coordinates of a position of the person's (100) hand and a state of each articulation and applies the signal to the graphics and world controller 112.
The graphics and world controller 112 determines how to change the world model 128 based on the information indicative of position/posture of the head and the hand of the person 100 and the information of the world model 128 representing the former virtual reality. The world model 128 is subjected to a predetermined processing based on the determination.
The stereo display controller 114 generates stereoscopic video to be applied to the person 100 according to a new world model 128. The stereoscopic video signals includes a pair of video, one for the person's right eye and the other for the left eye. The stereo display 116 alternately displays the video for the right eye and video for the left eye at predetermined intervals. The displayed virtual body 118 is reflected by the halfmirror 120, which reflection enters the eye of the person 100 as a virtual body 132. At this time, the synchronization signal transmitter 126 opens the right side shutter of the liquid crystal glass 104 when the video for a right eye is displayed and the left side shutter when the video for a left eye is displayed, with the other shutter closed. As a result, the video for a right eye and the video for a left eye are respectively applied to the right eye and the left eye of the person 100. The person 100 recognizes the virtual body 132 as being stereoscopic.
The force feedback controller 124 determines reactive force to be applied to the hand of the person 100 according to the world model 128. The force feedback controller 124 operates the force feedback head 122 based on the determined reactive force to press the hand of the person 100 with the data glove 106 put thereon. As a result, the person 100 feels as if he actually touched the virtual body 132.
It is clear that finding the accurate position of the person 100 is important for the above-described VR system. For this, one used as the space sensor 102 is shown in FIG. 2. With reference to FIG. 2, the position detection system includes a source coil 134, a sensor coil 136, a detection circuit 138, a computer 140 and a drive circuit 142. Each of the source coil 134 and the sensor coil 136 includes three Helmholtz coils arranged orthogonal to each other.
The three coils of the source coil 134 generate magnetic field in a time divisional manner. The sensor coil 136 senses the magnetic field generated by the source coil 134. The output of the sensor coil 136 is detected by the detection circuit 138 and applied to the computer 140. The computer 140 computes spatial position and posture of the sensor coil 136 based on nine pieces of information (3.times.3) obtained from the output of the sensor coil 136. The computed information is output through the computer 140.
The system shown in FIG. 2, however, has following shortcomings. First, the system is incapable of detecting a position of a body in the entire space. Second, the system operates so slowly that movements of virtual reality cannot be precisely changed in accordance with the user's movements. Furthermore, in the system, when a metallic body exists in measurement space, a magnetic field change caused by the metallic body leads to an error in a measured value.
The data glove 106 for use in the system shown in FIG. 1 can also measure coordinates of a tip of a finger, for example.
With reference to FIG. 3, the data glove 106 includes glove main body 144, a space sensor 146 attached to the back of the glove main body 144 such as shown in FIG. 2, and an optical fiber sensor 150 attached to the glove 144 along the respective fingers of the glove 144 by a fiber stopper 148. The optical fiber sensor 150 enables input equivalent to 2 degrees of freedom per finger, that is, the input equivalent to the total of 10 degrees of freedom to be obtained. Furthermore, an additional use of the space sensor 146 allows the data glove 106 to obtain information equivalent to 16 degrees of freedom including position/posture of the hand. Then, coordinates of a position of the tip of a predetermined finger can be specified by adding the output of the position sensor 146 and the multiplication of the output of the optical fiber sensor 150. Based on the same principle, a suit called a data suit has been made public which is capable of measuring movements of the entire body.
A device such as the data glove has an excellent function of converting minute movements into corresponding information. On the other hand, such device requires a power source to be supplied to a part itself for designating a spatial position and a sensor to be provided. As a result, the system is made large in scale as a whole. In addition, such device allows recognition of coordinates only in limited range of space.
Another attempt is a system as shown in FIG. 4. With reference to FIG. 4, the system includes a mouse pen 152 which can be freely moved in space by a person's hand and has a light emitting position 156, and two pairs of light receiving portions 154 for receiving a light from the light emitting portion 156. As each of the light receiving portions 154, a conventional camera can be used. The respective light receiving portions 154 in the system shown in FIG. 4 includes a lens 158 and a light receiving element 160. A filter 164 is provided on the light receiving element 160. The light receiving element 160 and the lens 158 are located to have their axes cross each other at a predetermined angle.
In the system shown in FIG. 4, a light from the light emitting portion 156 of the mouse pen 152 passes through the lenses 158 to enter the pair of light receiving elements 160. The incident angle of the light onto the light receiving element 160 is changed according to a position of the light emitting portion 156. The light incident angle can be found by the position of the image of the light emitting portion 156 formed on each light receiving element 160. A position of the light emitting portion 156 of the mouse pen 152 can be found based on the incident angle and a distance between the light receiving elements 160 on the principle of trigonometrical survey. The filter 164 serves to apply only light emitted from the light emitting portion 156, out of the incident lights, to the light receiving element 160.
The system shown in FIG. 4, however, requires two light receiving elements or cameras. This makes the device complicated and large in scale. In addition, when a distance between light receiving elements or cameras must be changed, it is difficult to adapt the system to new conditions with ease. Furthermore, the pen 152 for pointing out a specific point in space and having the light emitting portion 156 requires a power source to be provided therewith for operating the light emitting portion 156. In addition, the lens 158 and the light receiving element 160 arranged to have their axes crossing to each other at a predetermined angle has a narrow space wherein coordinates can be designated.